Embodiments of the invention relate generally to rotary devices and, more particularly, to systems, devices, and methods for shifting a torsional mode frequency of a rotary device.
Rotary devices are known to suffer from various vibration problems during their operation. One such vibration problem is torsional vibration. In all practical rotor systems there is no inherent ability to damper torsional vibration.
When a power train torsional mode is near to a continuous forcing function, such as twice a line frequency of a power generating unit (e.g., a steam turbine-generator system), torsional vibration may be so severe that continuous safe operation of the unit is not possible. Typically, this results in activation of a tripping system and the unit is shut down.
Currently, since the line frequency cannot be changed, torsional vibration is addressed by disassembling the device and shrink fitting a large number of rings on an outer surface of a rotor flange. The device is then reassembled and tested to confirm a reduction in torsional vibration. This process is both time consuming (typically 30-40 days) and consequently expensive, resulting in significant downtime for the device and a concomitant loss of revenue.